Experimental analysis and prediction of radionuclide solubility using machine learning models: Effects of organic complexing agents.

Radioactive wastes contain organic complexing agents that can form complexes with radionuclides and enhance the solubility of these radionuclides, increasing the mobility of radionuclides over great distances from a radioactive waste repository. In this study, four radionuclides (cobalt, strontium, iodine, and uranium) and three organic complexing agents (ethylenediaminetetraacetic acid, nitrilotriacetic acid, and iso-saccharic acid) were selected, and the solubility of these radionuclides was assessed under realistic environmental conditions such as different pHs (7, 9, 11, and 13), temperatures (10 °C, 20 °C, and 40 °C), and organic complexing agent concentrations (10-5-10-2 M). A total of 720 datasets were generated from solubility batch experiments. Four supervised machine learning models such as the Gaussian process regression (GPR), ensemble-boosted trees, artificial neural networks, and support vector machine were developed for predicting the radionuclide solubility. Each ML model was optimized using Bayesian optimization algorithm. The GPR evolved as a robust model that provided accurate predictions within the underlying solubility patterns by capturing the intricate relationships of the independent parameters of the dataset. At an uncertainty level of 95%, both the experimental results and GPR simulated estimations were closely correlated, confirming the suitability of the GPR model for future explorations.

Pore Parameters-Dependent Adsorption Behavior of Volatile Organic Compounds on Graphene-Based Material.

Mesoporous graphenes (MPGs) with interpenetrating porous networks are successfully obtained by the pyrolysis of composite gel consisting of graphite oxide (GO) and the amphiphilic triblock copolymer (Pluronic P123) under Ar atmosphere, wherein P123 is used as a soft-template. The as-prepared composite gel is obtained following self-assembly and freeze-drying. The obtained MPGs have high BET specific surface area (531-746 m2 g-1 and ink-bottle like pores with three dimensional interconnected network. Furthermore, the specific surface area and porous parameters such as pore volume, pore size, and pore size distribution of MPGs can be rationally controlled by regulating the initial mass ratio of P123 to GO. With the increase of P123 ratio, the average mesopore size is decreased from ∼16.4 nm to ∼9.5 nm, which is similar to the diameter size of P123 micelles. Also, the adsorption capacities of MPG-20 for 52 indoor air standard components (100 µg mL-1, Supelco) are compared with two different materials, namely commercial porous polymers (2,6-diphenyleneoxide) and reduced graphene oxide (RGO). The result shows that MPG-20 has significantly better adsorption capacity than RGO but also similar or slightly better than commercial porous polymer. The mesoporous structure and surface chemistry of MPGs were the most important factors for the enhancement of the adsorption efficiency for volatile organic compounds.

Two Distinctive Hierarchical Products through the Hydrothermal Process for ß-Co(OH)2 Reacting with NaH2PO2 and Their Morphological Effect on Electrochemical Hydrogen Storage.

This paper reports a study of the reaction behavior of ß-Co(OH)2 with NaH2PO2 under hydrothermal conditions, depending on the concentration of NaOH (0-9.0 M). Uniform sized ß-Co(OH)2 microplatelets, as the precursor, were prepared by the method of homogeneous precipitation using hydrolysis reaction with hexamethylenetetramine as the base. After the hydrothermal reaction, two distinctive products were obtained: cobalt phosphite [Co11(HPO3)8(OH)6] and hcp Co metal. The XRD analysis reveals that the Co11(HPO3)8(OH)6 appeared in the absence of NaOH. Then, Co11(HPO3)8(OH)6 and the hcp Co metal simultaneously appeared under 1.125 M NaOH. At 2.25-4.5 M NaOH, ß-Co(OH)2 and hcp Co metal appeared concurrently, and only pure hcp Co metal appeared under 9.0 M NaOH. The FE-SEM observations indicated that the obtained particles were dendritic-like Co11(HPO3)8(OH)6 and flower-like Co metal. We found that the solubility of ß-Co(OH)2 and the role of the NaH2PO2 were strongly influenced by the concentration of NaOH during this reaction. To investigate the morphological effect of the two obtained products on the electrochemical hydrogen storage performance, materials with the same crystal structures yet with different morphologies were used for comparison. The evaluations of electrochemical performance proved that the two products showed better reversibility, and higher storage capacity and rate dischargeability than the comparative materials. Their relatively good performances can be attributed to their morphology, which resulted in increased surface area, reduced diffusion pathway, and the accommodation of volume change during cycling.

Enhanced Cellular Uptake of Silica-Coated Magnetite Nanoparticles Compared with PEG-Coated Ones in Stem Cells.

Monodispersed magnetite (Fe3O4) nanoparticles (NPs) were prepared through the thermal decomposition method. The obtained NPs were surface modified with silica (SiO2) and polyethylene glycol (PEG), to enhance their stability in aqueous environment and their cellular uptake efficiency for biomedical applications. The NPs were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared (FT-IR) spectroscopy, and dynamic light scattering (DLS). The cytotoxicity of these NPs on bone marrow mesenchymal stem cells (BM-MSCs) was measured by MTT assay (cell viability test) at various concentrations (2, 5, 12.5, 25, and 50 µg/mL). The cells remained more than 90% viable at concentrations as high as 50 µg/mL. To compare the cellular uptake efficiency, these NPs were treated in BM-MSCs and the Fe concentration within the cells was measured by inductively coupled plasma-atomic emission spectrometry (ICP-AES) analysis. The uptake process displayed a time- and dose-dependency. The uptake amount of SiO2-coated Fe3O4 (Fe3O4@SiO2) NPs was about 10 times higher than that of the PEG-coated ones (Fe3O4@PEG).